Individual semiconductor (integrated circuit) devices (dies) are typically produced by creating several identical devices on a semiconductor wafer, using know techniques of photolithography, deposition, and the like. Generally, these processes are intended to create a plurality of fully-functional integrated circuit devices, prior to singulating (severing) the individual dies from the semiconductor wafer. In practice, however, certain physical defects in the wafer itself and certain defects in the processing of the wafer inevitably lead to some of the dies being "good" (fully-functional) and some of the dies being "bad" (non-functional). It is generally desirable to be able to identify which of the plurality of dies on a wafer are good dies prior to their packaging, and preferably prior to their being singulated from the wafer. To this end, a wafer "tester" or "prober" may advantageously be employed to make a plurality of discrete pressure connections to a like plurality of discrete connection pads (bond pads) on the dies. In this manner, the semiconductor dies can be tested and exercised, prior to singulating the dies from the wafer. A conventional component of a wafer tester is a "probe card" to which a plurality of probe elements are connected--tips of the probe elements effecting the pressure connections to the respective bond pads of the semiconductor dies.
Prior art probe card assemblies include a plurality of tungsten needles extending as cantilevers from a surface of a probe card. The tungsten needles may be mounted in any suitable manner to the probe card, such as by the intermediary of an epoxy ring, as discussed hereinabove. Generally, in any case, the needles are wired to terminals of the probe card through the intermediary of a separate and distinct wire connecting the needles to the terminals of the probe card.
Probe cards are typically formed as circular rings, with hundreds of probe elements (needles) extending from an inner periphery of the ring (and wired to terminals of the probe card). Circuit modules, and conductive traces (lines) of preferably equal length, are associated with each of the probe elements. This ring-shape layout makes it difficult, and in some cases impossible, to probe a plurality of unsingulated semiconductor dies (multiple sites) on a wafer, especially when the bond pads of each semiconductor die are arranged in other than two linear arrays along two opposite edges of the semiconductor die.
The aforementioned commonly-owned, copending PCT Patent Application No. US95/14844, a priority application to the present specification, published as WO 96/15458 May 23, 1996, discloses a probe card assembly which includes a probe card, a space transformer having resilient contact structures (probe elements) mounted directly to (i.e., without the need for additional connecting wires or the like) and extending from terminals on a surface thereof, and an interposer disposed between the space transformer and the probe card. The space transformer and interposer are "stacked up" so that the orientation of the space transformer, hence the orientation of the tips of the probe elements, can be adjusted without changing the orientation of the probe card. Suitable mechanisms for adjusting the orientation of the space transformer, and for determining what adjustments to make, are disclosed. The interposer has resilient contact structures extending from both the top and bottom surfaces thereof, and ensures that electrical connections are maintained between the space transformer and the probe card throughout the space transformer's range of adjustment, by virtue of the interposer's inherent compliance. Multiple die sites on a semiconductor wafer are readily probed using the disclosed techniques, and the probe elements can be arranged to optimize probing of an entire wafer. Composite interconnection elements having a relatively soft core overcoated by a relatively hard shell, as the resilient contact structures are described.
In the probe card assembly of US95/14844, the space transformer component conveys both signals and power to the semiconductor device(s) being probed. For probing (e.g., testing) certain high-power semiconductor devices, a relatively large amount of power required to drive the devices. In such a probe card assembly, both power and signals are conveyed to the space transformer component by an interposer component.